Typically, in engine cooling systems, a coolant pump comprises a pulley keyed to a shaft carrying a pump impeller which is driven by the engine via a belt and pulley coupling. Such pumps require fluid seals around the pump shaft which may present maintenance problems. Also, pump bearings are required, which often fail before other engine components. Failure of such components is sometimes due to the side load on bearings and seals from the belt and pulley drive, which tends to allow pressurized coolant to leak out of the system and cause bearing seizure.
These typical prior art pumps are also directly integrated with engine rpm via gears or pulleys, and thus flow rate is not controllable. Also, these pumps typically comprise low efficiency centrifugal impellers. They are also limited in where they can be mounted on the engine due to the requirement of connection to the engine drive.
U.S. Pat. No. 5,079,488 describes one attempt to overcome the shortcomings of prior art coolant pumps. The '488 patent provides an electronically commutated pump for pumping fluid in a vehicle coolant system which eliminates the need for fluid seals and eliminates non-symmetrical side loads. However, the invention described in the '488 patent is costly and inefficient in that it only provides flow rate in the range of five gallons per minute at 3000 rpm, and does not provide sufficient fluid pressure for engine coolant applications. The large impeller axle assembly of the '488 patent adds substantial cost to the product while significantly reducing fluid flow capacity, as well as pressure. Finally, the '488 patent uses magnets as part of the drive system which are expensive and degrade with heat and time.
Accordingly, it is desirable to provide an improved fluid pump which overcomes the above-referenced shortcomings of typical prior art mechanical pumps, while also providing enhanced fluid flow rate and control capability while reducing costs.